The present disclosure relates to image-capturing devices that capture an image (range image) of an object located at a certain distance, and more particularly, to an image-capturing device that captures a normal image (visible light image) along with a range image, and a method for driving the device.
A ranging camera (motion camera) that illuminates a space where shooting is performed with, for example, infrared light to detect a motion of the body or hand of an object (human subject), has in recent years been included in a television, game device, and the like. Such a ranging camera includes an image-capturing device known as a ranging sensor that obtains a range image for use in the ranging camera.
If the ranging sensor can obtain a normal visible light image as well as a range image simultaneously, this is effective in extracting a specific object from the image (background subtraction), producing a three-dimensional image, etc.
Japanese Unexamined Patent Publication No. 2008-8700 describes a single solid-state image-capturing device that simultaneously obtains a range image and a visible light image. Specifically, the solid-state image-capturing device includes a single sensor that can capture images using visible light and infrared (IR) light. The solid-state image-capturing device illuminates a space where shooting is performed with an IR pulse every other frame scanning period while capturing images using visible light and infrared light every frame scanning period. By producing a visible light image every frame scanning period and subtracting an IR pixel signal obtained by shooting in the absence of illumination with an IR pulse from an IR pixel signal obtained by shooting in the presence of illumination with an IR pulse, a range image from which an influence of background light has been removed is produced every other frame scanning period.
However, in the above solid-state image-capturing device, a plurality of frames are used to produce a range image from which an influence of background light has been removed, and therefore, if an object moves between two successive frames, an error occurs in a range image. Also, a plurality of frames are required to obtain each single range image as described above, the frame rate of range images is reduced. Therefore, there is a problem that distance information of a moving object cannot be accurately obtained.